The regulation of PRL secretion in various hyperprolactinemic states will be evaluated with a 24 hr profile, dopamine infusion, TRH stim and metoclopramide stim testing. Emphasis will be placed on patients hypersecreting 150,000K PRL. Column chromatography and NB2 bioassay will be used to evaluate various molecular weight PRL release. Frequency and natural history of macroprolactinemia will be established. Family members will be evaluated for macroprolactinemia to correlate genetic aspects of this disease.